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ClickHouse/src/Common/Volnitsky.h
Robert Schulze bb7c627964
Cosmetics: Pass patterns around as std::string_view instead of StringRef 
- The patterns are not used in hashing, there should not be a performance
  impact when we use stuff from the standard library instead.

- added forgotten .reserve() in FunctionsMultiStringPosition.h
2022-06-26 15:32:19 +00:00

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#pragma once
#include <algorithm>
#include <vector>
#include <stdint.h>
#include <string.h>
#include <base/types.h>
#include <Poco/Unicode.h>
#include <Common/StringSearcher.h>
#include <Common/StringUtils/StringUtils.h>
#include <Common/UTF8Helpers.h>
#include <base/StringRef.h>
#include <base/unaligned.h>
/** Search for a substring in a string by Volnitsky's algorithm
* http://volnitsky.com/project/str_search/
*
* `haystack` and `needle` can contain zero bytes.
*
* Algorithm:
* - if the `needle` is too small or too large, or too small `haystack`, use std::search or memchr;
* - when initializing, fill in an open-addressing linear probing hash table of the form
* hash from the bigram of needle -> the position of this bigram in needle + 1.
* (one is added only to distinguish zero offset from an empty cell)
* - the keys are not stored in the hash table, only the values are stored;
* - bigrams can be inserted several times if they occur in the needle several times;
* - when searching, take from haystack bigram, which should correspond to the last bigram of needle (comparing from the end);
* - look for it in the hash table, if found - get the offset from the hash table and compare the string bytewise;
* - if it did not match, we check the next cell of the hash table from the collision resolution chain;
* - if not found, skip to haystack almost the size of the needle bytes;
*
* MultiVolnitsky - search for multiple substrings in a string:
* - Add bigrams to hash table with string index. Then the usual Volnitsky search is used.
* - We are adding while searching, limiting the number of fallback searchers and the total number of added bigrams
*/
namespace DB
{
namespace VolnitskyTraits
{
using Offset = UInt8; /// Offset in the needle. For the basic algorithm, the length of the needle must not be greater than 255.
using Id = UInt8; /// Index of the string (within the array of multiple needles), must not be greater than 255.
using Ngram = UInt16; /// n-gram (2 bytes).
/** Fits into the L2 cache (of common Intel CPUs).
* This number is extremely good for compilers as it is numeric_limits<Uint16>::max() and there are optimizations with movzwl and other instructions with 2 bytes
*/
static constexpr size_t hash_size = 64 * 1024;
/// min haystack size to use main algorithm instead of fallback
static constexpr size_t min_haystack_size_for_algorithm = 20000;
static inline bool isFallbackNeedle(const size_t needle_size, size_t haystack_size_hint = 0)
{
return needle_size < 2 * sizeof(Ngram) || needle_size >= std::numeric_limits<Offset>::max()
|| (haystack_size_hint && haystack_size_hint < min_haystack_size_for_algorithm);
}
static inline Ngram toNGram(const UInt8 * const pos) { return unalignedLoad<Ngram>(pos); }
template <typename Callback>
static inline bool putNGramASCIICaseInsensitive(const UInt8 * pos, int offset, Callback && putNGramBase)
{
struct Chars
{
UInt8 c0;
UInt8 c1;
};
union
{
Ngram n;
Chars chars;
};
n = toNGram(pos);
const auto c0_al = isAlphaASCII(chars.c0);
const auto c1_al = isAlphaASCII(chars.c1);
if (c0_al && c1_al)
{
/// 4 combinations: AB, aB, Ab, ab
putNGramBase(n, offset);
chars.c0 = alternateCaseIfAlphaASCII(chars.c0);
putNGramBase(n, offset);
chars.c1 = alternateCaseIfAlphaASCII(chars.c1);
putNGramBase(n, offset);
chars.c0 = alternateCaseIfAlphaASCII(chars.c0);
putNGramBase(n, offset);
}
else if (c0_al)
{
/// 2 combinations: A1, a1
putNGramBase(n, offset);
chars.c0 = alternateCaseIfAlphaASCII(chars.c0);
putNGramBase(n, offset);
}
else if (c1_al)
{
/// 2 combinations: 0B, 0b
putNGramBase(n, offset);
chars.c1 = alternateCaseIfAlphaASCII(chars.c1);
putNGramBase(n, offset);
}
else
/// 1 combination: 01
putNGramBase(n, offset);
return true;
}
template <typename Callback>
static inline bool putNGramUTF8CaseInsensitive(
const UInt8 * pos, int offset, const UInt8 * begin, size_t size, Callback && putNGramBase)
{
const UInt8 * end = begin + size;
struct Chars
{
UInt8 c0;
UInt8 c1;
};
union
{
VolnitskyTraits::Ngram n;
Chars chars;
};
n = toNGram(pos);
if (isascii(chars.c0) && isascii(chars.c1))
{
return putNGramASCIICaseInsensitive(pos, offset, putNGramBase);
}
else
{
/** n-gram (in the case of n = 2)
* can be entirely located within one code point,
* or intersect with two code points.
*
* In the first case, you need to consider up to two alternatives - this code point in upper and lower case,
* and in the second case - up to four alternatives - fragments of two code points in all combinations of cases.
*
* It does not take into account the dependence of the case-transformation from the locale (for example - Turkish `Ii`)
* as well as composition / decomposition and other features.
*
* It also does not work if characters with lower and upper cases are represented by different number of bytes or code points.
*/
using Seq = UInt8[6];
if (UTF8::isContinuationOctet(chars.c1))
{
/// ngram is inside a sequence
const auto * seq_pos = pos;
UTF8::syncBackward(seq_pos, begin);
auto u32 = UTF8::convertUTF8ToCodePoint(seq_pos, end - seq_pos);
/// Invalid UTF-8
if (!u32)
{
putNGramBase(n, offset);
}
else
{
int l_u32 = Poco::Unicode::toLower(*u32);
int u_u32 = Poco::Unicode::toUpper(*u32);
/// symbol is case-independent
if (l_u32 == u_u32)
{
putNGramBase(n, offset);
}
else
{
/// where is the given ngram in respect to the start of UTF-8 sequence?
size_t seq_ngram_offset = pos - seq_pos;
Seq seq_l;
size_t length_l = UTF8::convertCodePointToUTF8(l_u32, seq_l, sizeof(seq_l));
Seq seq_r;
size_t length_r = UTF8::convertCodePointToUTF8(u_u32, seq_r, sizeof(seq_r));
if (length_l != length_r)
return false;
assert(length_l >= 2 && length_r >= 2);
chars.c0 = seq_l[seq_ngram_offset];
chars.c1 = seq_l[seq_ngram_offset + 1];
putNGramBase(n, offset);
chars.c0 = seq_r[seq_ngram_offset]; //-V519
chars.c1 = seq_r[seq_ngram_offset + 1]; //-V519
putNGramBase(n, offset);
}
}
}
else
{
/// ngram is on the boundary of two sequences
/// first sequence may start before u_pos if it is not ASCII
const auto * first_seq_pos = pos;
UTF8::syncBackward(first_seq_pos, begin);
/// where is the given ngram in respect to the start of first UTF-8 sequence?
size_t seq_ngram_offset = pos - first_seq_pos;
auto first_u32 = UTF8::convertUTF8ToCodePoint(first_seq_pos, end - first_seq_pos);
int first_l_u32 = 0;
int first_u_u32 = 0;
if (first_u32)
{
first_l_u32 = Poco::Unicode::toLower(*first_u32);
first_u_u32 = Poco::Unicode::toUpper(*first_u32);
}
/// second sequence always start immediately after u_pos
const auto * second_seq_pos = pos + 1;
auto second_u32 = UTF8::convertUTF8ToCodePoint(second_seq_pos, end - second_seq_pos);
int second_l_u32 = 0;
int second_u_u32 = 0;
if (second_u32)
{
second_l_u32 = Poco::Unicode::toLower(*second_u32);
second_u_u32 = Poco::Unicode::toUpper(*second_u32);
}
/// both symbols are case-independent
if (first_l_u32 == first_u_u32 && second_l_u32 == second_u_u32)
{
putNGramBase(n, offset);
}
else if (first_l_u32 == first_u_u32)
{
/// first symbol is case-independent
Seq seq_l;
size_t size_l = UTF8::convertCodePointToUTF8(second_l_u32, seq_l, sizeof(seq_l));
Seq seq_u;
size_t size_u = UTF8::convertCodePointToUTF8(second_u_u32, seq_u, sizeof(seq_u));
if (size_l != size_u)
return false;
assert(size_l >= 1 && size_u >= 1);
chars.c1 = seq_l[0];
putNGramBase(n, offset);
/// put ngram from uppercase, if it is different
if (chars.c1 != seq_u[0])
{
chars.c1 = seq_u[0];
putNGramBase(n, offset);
}
}
else if (second_l_u32 == second_u_u32)
{
/// second symbol is case-independent
Seq seq_l;
size_t size_l = UTF8::convertCodePointToUTF8(first_l_u32, seq_l, sizeof(seq_l));
Seq seq_u;
size_t size_u = UTF8::convertCodePointToUTF8(first_u_u32, seq_u, sizeof(seq_u));
if (size_l != size_u)
return false;
assert(size_l > seq_ngram_offset && size_u > seq_ngram_offset);
chars.c0 = seq_l[seq_ngram_offset];
putNGramBase(n, offset);
/// put ngram for uppercase, if it is different
if (chars.c0 != seq_u[seq_ngram_offset])
{
chars.c0 = seq_u[seq_ngram_offset];
putNGramBase(n, offset);
}
}
else
{
Seq first_l_seq;
Seq first_u_seq;
Seq second_l_seq;
Seq second_u_seq;
size_t size_first_l = UTF8::convertCodePointToUTF8(first_l_u32, first_l_seq, sizeof(first_l_seq));
size_t size_first_u = UTF8::convertCodePointToUTF8(first_u_u32, first_u_seq, sizeof(first_u_seq));
size_t size_second_l = UTF8::convertCodePointToUTF8(second_l_u32, second_l_seq, sizeof(second_l_seq));
size_t size_second_u = UTF8::convertCodePointToUTF8(second_u_u32, second_u_seq, sizeof(second_u_seq));
if (size_first_l != size_first_u || size_second_l != size_second_u)
return false;
assert(size_first_l > seq_ngram_offset);
assert(size_first_u > seq_ngram_offset);
assert(size_second_l > 0);
assert(size_second_u > 0);
auto c0l = first_l_seq[seq_ngram_offset];
auto c0u = first_u_seq[seq_ngram_offset];
auto c1l = second_l_seq[0];
auto c1u = second_u_seq[0];
/// ngram for ll
chars.c0 = c0l;
chars.c1 = c1l;
putNGramBase(n, offset);
if (c0l != c0u)
{
/// ngram for Ul
chars.c0 = c0u;
chars.c1 = c1l; //-V1048
putNGramBase(n, offset);
}
if (c1l != c1u)
{
/// ngram for lU
chars.c0 = c0l;
chars.c1 = c1u;
putNGramBase(n, offset);
}
if (c0l != c0u && c1l != c1u)
{
/// ngram for UU
chars.c0 = c0u;
chars.c1 = c1u;
putNGramBase(n, offset);
}
}
}
}
return true;
}
template <bool CaseSensitive, bool ASCII, typename Callback>
static inline bool putNGram(const UInt8 * pos, int offset, [[maybe_unused]] const UInt8 * begin, size_t size, Callback && putNGramBase)
{
if constexpr (CaseSensitive)
{
putNGramBase(toNGram(pos), offset);
return true;
}
else if constexpr (ASCII)
{
return putNGramASCIICaseInsensitive(pos, offset, std::forward<Callback>(putNGramBase));
}
else
{
return putNGramUTF8CaseInsensitive(pos, offset, begin, size, std::forward<Callback>(putNGramBase));
}
}
}
/// @todo store lowercase needle to speed up in case there are numerous occurrences of bigrams from needle in haystack
template <bool CaseSensitive, bool ASCII, typename FallbackSearcher>
class VolnitskyBase
{
protected:
const UInt8 * needle;
size_t needle_size;
const UInt8 * needle_end = needle + needle_size;
/// For how long we move, if the n-gram from haystack is not found in the hash table.
size_t step = needle_size - sizeof(VolnitskyTraits::Ngram) + 1;
/** max needle length is 255, max distinct ngrams for case-sensitive is (255 - 1), case-insensitive is 4 * (255 - 1)
* storage of 64K ngrams (n = 2, 128 KB) should be large enough for both cases */
std::unique_ptr<VolnitskyTraits::Offset[]> hash; /// Hash table.
bool fallback; /// Do we need to use the fallback algorithm.
FallbackSearcher fallback_searcher;
public:
using Searcher = FallbackSearcher;
/** haystack_size_hint - the expected total size of the haystack for `search` calls. Optional (zero means unspecified).
* If you specify it small enough, the fallback algorithm will be used,
* since it is considered that it's useless to waste time initializing the hash table.
*/
VolnitskyBase(const char * const needle_, const size_t needle_size_, size_t haystack_size_hint = 0)
: needle{reinterpret_cast<const UInt8 *>(needle_)}
, needle_size{needle_size_}
, fallback{VolnitskyTraits::isFallbackNeedle(needle_size, haystack_size_hint)}
, fallback_searcher{needle_, needle_size}
{
if (fallback || fallback_searcher.force_fallback)
return;
hash = std::unique_ptr<VolnitskyTraits::Offset[]>(new VolnitskyTraits::Offset[VolnitskyTraits::hash_size]{});
auto callback = [this](const VolnitskyTraits::Ngram ngram, const int offset) { return this->putNGramBase(ngram, offset); };
/// ssize_t is used here because unsigned can't be used with condition like `i >= 0`, unsigned always >= 0
/// And also adding from the end guarantees that we will find first occurrence because we will lookup bigger offsets first.
for (auto i = static_cast<ssize_t>(needle_size - sizeof(VolnitskyTraits::Ngram)); i >= 0; --i)
{
bool ok = VolnitskyTraits::putNGram<CaseSensitive, ASCII>(needle + i, i + 1, needle, needle_size, callback);
/** `putNGramUTF8CaseInsensitive` does not work if characters with lower and upper cases
* are represented by different number of bytes or code points.
* So, use fallback if error occurred.
*/
if (!ok)
{
fallback_searcher.force_fallback = true;
hash = nullptr;
return;
}
}
}
/// If not found, the end of the haystack is returned.
const UInt8 * search(const UInt8 * const haystack, const size_t haystack_size) const
{
if (needle_size == 0)
return haystack;
const auto * haystack_end = haystack + haystack_size;
if (fallback || haystack_size <= needle_size || fallback_searcher.force_fallback)
return fallback_searcher.search(haystack, haystack_end);
/// Let's "apply" the needle to the haystack and compare the n-gram from the end of the needle.
const auto * pos = haystack + needle_size - sizeof(VolnitskyTraits::Ngram);
for (; pos <= haystack_end - needle_size; pos += step)
{
/// We look at all the cells of the hash table that can correspond to the n-gram from haystack.
for (size_t cell_num = VolnitskyTraits::toNGram(pos) % VolnitskyTraits::hash_size; hash[cell_num];
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size)
{
/// When found - compare bytewise, using the offset from the hash table.
const auto * res = pos - (hash[cell_num] - 1);
/// pointer in the code is always padded array so we can use pagesafe semantics
if (fallback_searcher.compare(haystack, haystack_end, res))
return res;
}
}
return fallback_searcher.search(pos - step + 1, haystack_end);
}
const char * search(const char * haystack, size_t haystack_size) const
{
return reinterpret_cast<const char *>(search(reinterpret_cast<const UInt8 *>(haystack), haystack_size));
}
protected:
void putNGramBase(const VolnitskyTraits::Ngram ngram, const int offset)
{
/// Put the offset for the n-gram in the corresponding cell or the nearest free cell.
size_t cell_num = ngram % VolnitskyTraits::hash_size;
while (hash[cell_num])
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size; /// Search for the next free cell.
hash[cell_num] = offset;
}
};
template <bool CaseSensitive, bool ASCII, typename FallbackSearcher>
class MultiVolnitskyBase
{
private:
/// needles and their offsets
const std::vector<std::string_view> & needles;
/// fallback searchers
std::vector<size_t> fallback_needles;
std::vector<FallbackSearcher> fallback_searchers;
/// because std::pair<> is not POD
struct OffsetId
{
VolnitskyTraits::Id id;
VolnitskyTraits::Offset off;
};
std::unique_ptr<OffsetId[]> hash;
/// step for each bunch of strings
size_t step;
/// last index of offsets that was not processed
size_t last;
/// limit for adding to hashtable. In worst case with case insentive search, the table will be filled at most as half
static constexpr size_t small_limit = VolnitskyTraits::hash_size / 8;
public:
explicit MultiVolnitskyBase(const std::vector<std::string_view> & needles_) : needles{needles_}, step{0}, last{0}
{
fallback_searchers.reserve(needles.size());
hash = std::unique_ptr<OffsetId[]>(new OffsetId[VolnitskyTraits::hash_size]); /// No zero initialization, it will be done later.
}
/**
* This function is needed to initialize hash table
* Returns `true` if there is nothing to initialize
* and `false` if we have something to initialize and initializes it.
* This function is a kind of fallback if there are many needles.
* We actually destroy the hash table and initialize it with uninitialized needles
* and search through the haystack again.
* The actual usage of this function is like this:
* while (hasMoreToSearch())
* {
* search inside the haystack with the known needles
* }
*/
bool hasMoreToSearch()
{
if (last == needles.size())
return false;
memset(hash.get(), 0, VolnitskyTraits::hash_size * sizeof(OffsetId));
fallback_needles.clear();
step = std::numeric_limits<size_t>::max();
size_t buf = 0;
size_t size = needles.size();
for (; last < size; ++last)
{
const char * cur_needle_data = needles[last].data();
const size_t cur_needle_size = needles[last].size();
/// save the indices of fallback searchers
if (VolnitskyTraits::isFallbackNeedle(cur_needle_size))
{
fallback_needles.push_back(last);
}
else
{
/// put all bigrams
auto callback = [this](const VolnitskyTraits::Ngram ngram, const int offset)
{
return this->putNGramBase(ngram, offset, this->last);
};
buf += cur_needle_size - sizeof(VolnitskyTraits::Ngram) + 1;
/// this is the condition when we actually need to stop and start searching with known needles
if (buf > small_limit)
break;
step = std::min(step, cur_needle_size - sizeof(VolnitskyTraits::Ngram) + 1);
for (auto i = static_cast<int>(cur_needle_size - sizeof(VolnitskyTraits::Ngram)); i >= 0; --i)
{
VolnitskyTraits::putNGram<CaseSensitive, ASCII>(
reinterpret_cast<const UInt8 *>(cur_needle_data) + i,
i + 1,
reinterpret_cast<const UInt8 *>(cur_needle_data),
cur_needle_size,
callback);
}
}
fallback_searchers.emplace_back(cur_needle_data, cur_needle_size);
}
return true;
}
inline bool searchOne(const UInt8 * haystack, const UInt8 * haystack_end) const
{
const size_t fallback_size = fallback_needles.size();
for (size_t i = 0; i < fallback_size; ++i)
if (fallback_searchers[fallback_needles[i]].search(haystack, haystack_end) != haystack_end)
return true;
/// check if we have one non empty volnitsky searcher
if (step != std::numeric_limits<size_t>::max())
{
const auto * pos = haystack + step - sizeof(VolnitskyTraits::Ngram);
for (; pos <= haystack_end - sizeof(VolnitskyTraits::Ngram); pos += step)
{
for (size_t cell_num = VolnitskyTraits::toNGram(pos) % VolnitskyTraits::hash_size; hash[cell_num].off;
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size)
{
if (pos >= haystack + hash[cell_num].off - 1)
{
const auto res = pos - (hash[cell_num].off - 1);
const size_t ind = hash[cell_num].id;
if (res + needles[ind].size() <= haystack_end && fallback_searchers[ind].compare(haystack, haystack_end, res))
return true;
}
}
}
}
return false;
}
inline size_t searchOneFirstIndex(const UInt8 * haystack, const UInt8 * haystack_end) const
{
const size_t fallback_size = fallback_needles.size();
size_t answer = std::numeric_limits<size_t>::max();
for (size_t i = 0; i < fallback_size; ++i)
if (fallback_searchers[fallback_needles[i]].search(haystack, haystack_end) != haystack_end)
answer = std::min(answer, fallback_needles[i]);
/// check if we have one non empty volnitsky searcher
if (step != std::numeric_limits<size_t>::max())
{
const auto * pos = haystack + step - sizeof(VolnitskyTraits::Ngram);
for (; pos <= haystack_end - sizeof(VolnitskyTraits::Ngram); pos += step)
{
for (size_t cell_num = VolnitskyTraits::toNGram(pos) % VolnitskyTraits::hash_size; hash[cell_num].off;
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size)
{
if (pos >= haystack + hash[cell_num].off - 1)
{
const auto res = pos - (hash[cell_num].off - 1);
const size_t ind = hash[cell_num].id;
if (res + needles[ind].size() <= haystack_end && fallback_searchers[ind].compare(haystack, haystack_end, res))
answer = std::min(answer, ind);
}
}
}
}
/*
* if nothing was found, answer + 1 will be equal to zero and we can
* assign it into the result because we need to return the position starting with one
*/
return answer + 1;
}
template <typename CountCharsCallback>
inline UInt64 searchOneFirstPosition(const UInt8 * haystack, const UInt8 * haystack_end, const CountCharsCallback & count_chars) const
{
const size_t fallback_size = fallback_needles.size();
UInt64 answer = std::numeric_limits<UInt64>::max();
for (size_t i = 0; i < fallback_size; ++i)
if (auto pos = fallback_searchers[fallback_needles[i]].search(haystack, haystack_end); pos != haystack_end)
answer = std::min<UInt64>(answer, pos - haystack);
/// check if we have one non empty volnitsky searcher
if (step != std::numeric_limits<size_t>::max())
{
const auto * pos = haystack + step - sizeof(VolnitskyTraits::Ngram);
for (; pos <= haystack_end - sizeof(VolnitskyTraits::Ngram); pos += step)
{
for (size_t cell_num = VolnitskyTraits::toNGram(pos) % VolnitskyTraits::hash_size; hash[cell_num].off;
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size)
{
if (pos >= haystack + hash[cell_num].off - 1)
{
const auto res = pos - (hash[cell_num].off - 1);
const size_t ind = hash[cell_num].id;
if (res + needles[ind].size() <= haystack_end && fallback_searchers[ind].compare(haystack, haystack_end, res))
answer = std::min<UInt64>(answer, res - haystack);
}
}
}
}
if (answer == std::numeric_limits<UInt64>::max())
return 0;
return count_chars(haystack, haystack + answer);
}
template <typename CountCharsCallback, typename AnsType>
inline void searchOneAll(const UInt8 * haystack, const UInt8 * haystack_end, AnsType * answer, const CountCharsCallback & count_chars) const
{
const size_t fallback_size = fallback_needles.size();
for (size_t i = 0; i < fallback_size; ++i)
{
const UInt8 * ptr = fallback_searchers[fallback_needles[i]].search(haystack, haystack_end);
if (ptr != haystack_end)
answer[fallback_needles[i]] = count_chars(haystack, ptr);
}
/// check if we have one non empty volnitsky searcher
if (step != std::numeric_limits<size_t>::max())
{
const auto * pos = haystack + step - sizeof(VolnitskyTraits::Ngram);
for (; pos <= haystack_end - sizeof(VolnitskyTraits::Ngram); pos += step)
{
for (size_t cell_num = VolnitskyTraits::toNGram(pos) % VolnitskyTraits::hash_size; hash[cell_num].off;
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size)
{
if (pos >= haystack + hash[cell_num].off - 1)
{
const auto * res = pos - (hash[cell_num].off - 1);
const size_t ind = hash[cell_num].id;
if (answer[ind] == 0
&& res + needles[ind].size() <= haystack_end
&& fallback_searchers[ind].compare(haystack, haystack_end, res))
answer[ind] = count_chars(haystack, res);
}
}
}
}
}
void putNGramBase(const VolnitskyTraits::Ngram ngram, const int offset, const size_t num)
{
size_t cell_num = ngram % VolnitskyTraits::hash_size;
while (hash[cell_num].off)
cell_num = (cell_num + 1) % VolnitskyTraits::hash_size;
hash[cell_num] = {static_cast<VolnitskyTraits::Id>(num), static_cast<VolnitskyTraits::Offset>(offset)};
}
};
using Volnitsky = VolnitskyBase<true, true, ASCIICaseSensitiveStringSearcher>;
using VolnitskyUTF8 = VolnitskyBase<true, false, ASCIICaseSensitiveStringSearcher>; /// exactly same as Volnitsky
using VolnitskyCaseInsensitive = VolnitskyBase<false, true, ASCIICaseInsensitiveStringSearcher>; /// ignores non-ASCII bytes
using VolnitskyCaseInsensitiveUTF8 = VolnitskyBase<false, false, UTF8CaseInsensitiveStringSearcher>;
using VolnitskyCaseSensitiveToken = VolnitskyBase<true, true, ASCIICaseSensitiveTokenSearcher>;
using VolnitskyCaseInsensitiveToken = VolnitskyBase<false, true, ASCIICaseInsensitiveTokenSearcher>;
using MultiVolnitsky = MultiVolnitskyBase<true, true, ASCIICaseSensitiveStringSearcher>;
using MultiVolnitskyUTF8 = MultiVolnitskyBase<true, false, ASCIICaseSensitiveStringSearcher>;
using MultiVolnitskyCaseInsensitive = MultiVolnitskyBase<false, true, ASCIICaseInsensitiveStringSearcher>;
using MultiVolnitskyCaseInsensitiveUTF8 = MultiVolnitskyBase<false, false, UTF8CaseInsensitiveStringSearcher>;
}
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